1. Field of the Invention
The invention is directed to a hybrid vehicle drive for a motor vehicle.
2. Description of the Related Art
The irregularity or unevenness of the rotation of the crankshaft in conventional reciprocating-piston internal combustion engines excites torsional vibrations in the drivetrain conducting the torque from the internal combustion engine to the driving wheels of a motor vehicle. These torsional vibrations manifest themselves as undesirable shaking movements or at least as noise. Torsional vibrations of this kind are customarily damped by torsional vibration dampers that are integrated in the clutch disk of a clutch in the drivetrain. Since the torsional vibrations occur in the drivetrain in a resonant manner within a relatively large range of operating rates of rotation, conventional torsional vibration dampers of this type usually have a plurality of spring stages and friction devices dimensioned for various torque ranges. The torsional vibration dampers are therefore comparatively elaborate and are also frequently susceptible to malfunctions.
Starter-generators are electrical machines that can be operated as an electric motor or as a generator. German reference DE 32 30 607 C2 discloses a prior art starter-generator that is coupled with the crankshaft of a combustion engine and is utilized for active vibration damping. The prior art starter-generator operates as a generator when the motor vehicle is driven by an internal combustion engine. In this configuration, the starter-generator applies a load torque to the internal combustion engine while it charges a battery in the motor vehicle. The amount of load torque depends on its exciting current. A regulating circuit which responds to the torsional vibrations superposed on the rotation of the crankshaft and controls the exciting current of the electric machine such that the vibrations are regulated to a predetermined reference value. The reference variable or command variable of this regulating circuit representing the actual value is obtained by a differential element from the rate of rotation of the engine detected by a tachometer or speed sensor.
German references DE 40 15 701 and DE 43 23 601 disclose parallel hybrid drives for a motor vehicle in which the electric machine intended for the vehicle drive of the motor vehicle is utilized in addition to the internal combustion engine for active vibration damping. In this case also, the load torque exerted on the internal combustion engine by the electric machine is utilized for purposes of active vibration damping of torsional vibrations. However, it has been shown that the damping behavior of conventional active vibration dampers has often not achieved the standard previously achieved with mechanical vibration dampers.